1. Field of the Invention
The present invention relates to a device having quantum-wave interference layers that reflect carriers, or electrons and holes, effectively. In particular, the invention relates to light-emitting semiconductor devices including a laser (LD) and a light-emitting diode (LED) with improved luminous efficiency by effectively confining carriers within an active layer. Further, the present invention relates to semiconductor devices including a field effect transistor (FET) and a solar cell with improved carrier reflectivity.
2. Description of the Related Art
An LD has been known to have a double hetero junction structure whose active layer is formed between n-type and p-type cladding layers. The cladding layers function as potential barriers for effectively confining carriers, or electrons and holes, within the active layer.
However, a problem persists in luminous efficiency. Carriers overflow the potential barriers of the cladding layers, which lowers luminous efficiency. Therefore, further improvement has been required, as presently appreciated by the present inventors.
As a countermeasure, forming cladding layers with a multi-quantum well structure of a first and a second layers as a unit has been suggested by Takagi et al. (Japanese Journal of Applied Physics. Vol. 29, No. 11, November 1990, pp. L1977-L1980). This reference, however, does not teach or suggest values of kinetic energy of carriers to be considered and the degree of luminous intensity improvement is inadequate.